[PSUBS-MAILIST] Bladder oil compensation : was illustration is this what you mean sort of?? pressurized oil compensation bladder for motors

[MerlinSub@t-online.de]

Alan and the other gentlemens, 

our expierence with oil filled motors, batterys or even propeller shafts is that the oil expand if the motor is runing longer time. 
Simple because its warm up. We had that problem on Eurosub on the first dives. 
And on Euronaut we filled the bladder complet up and the get pretty hard in the hot summer just by sun heating the sub. 
A full filled bladder with over pressure creates a lot of interal 
pressure in the wrong direct - a lot of force for the bladder itself and hose work. 

Therefore our bladder are only half expand during the filling. But still free of any air. 
An other point is that the bladder has to be not to small.

To create a slightly overpressure on the motorseal you just install the bladder below the motorcasing. 
But we found out that on trolling motor (electric outboards) this is not nessesary. There seals are good for some 
douzend feets at least - so you can install the bladder else were. 
Filling is simpler if the bladder is slightly over the motor - you can vent the system direct on the filling point.

Another point is that we install now one bladder per motor  - in the earlier sub (Sgt.Peppers) we install a central
one for all motors. Hard to find a leak after a dive with all the T-crossing piepings and motorseals.. 

vbr Carsten


"Alan James" <alanjames@xtra.co.nz> schrieb:
> Hi Lawrie,
> from what I can understand of the explanation on oil compensating a motor on the ROV site is this....
> If you have a motor with half pie reasonable seals, you just fill it with a suitable low viscosity oil.
> You have a drain nipple in to the bottom of the motor casing & a nipple for attachment of a hose
> on the top of the casing. You attach a tube from the top nipple to a bellows or as they suggested
> something like the bladder in a football. This is filled with oil & pressurized to about 15 psi so there
> is always an external pressure of the motor oil over the internal pressure of the sea or lake water of
> 15 psi no matter what depth you are at. You can use the one bladder for all your motors.
> The other option they mentioned was in the case where the motor might not be designed for underwater
> applications & the seal not so good. In this case you can make an enclosure, put a suitable shaft seal
> in the enclosure & do the same as the first option with the nipples tube & bladder but on the enclosure
> not the motor. The motor inside would need to be filled with oil & have an opening in it. There shouldn't be
> any air in these systems.
> The idea of the seals back to back seems to be an additional option as a safe guard.
> I bought a couple of trawling motors that I couldn't easily change the seals on so will be trying the oil
> bladder method & if I'm going through too much oil then maybe air compensation or buying some better motors.
> Regards Alan
> 
> ----- Original Message ----- 
>   From: lawrie-psubs@environics.com.au
>   To: personal_submersibles@psubs.org
>   Sent: Sunday, December 05, 2010 2:53 PM
>   Subject: [PSUBS-MAILIST] illustration is this what you mean sort of?? pressurized oil compensation bladder for motors
> 
> 
>   Jim I created an illustration based on your concept as in outer oil housing and internal air housing for eletric motor.
> 
>   I have shown the location for  a pressure sensor within the closed stem at the top of the outer housing and at the bottom a stem 
> for the drain/fill/pressure up component not shown.
> 
>   Is this sort of what you mean with regards to seals and using oil to indicate you water passing the seal and increasing the 
> differential pressure between the two housings?  Lawrie
> 
> 
> 
>   On Fri, 3 Dec 2010 22:48:55 -0500 (EST), JimToddPsub@aol.com wrote:
> 
>     Great sites, Alan.  Thanks!
> 
>     Lots of supplies/components when you click on the COMPANIES button.
> 
>     Jim
> 
>     In a message dated 12/3/2010 8:29:18 P.M. Central Standard Time, alanjames@xtra.co.nz writes:
>       Dan Fjellroth's website is a good resource for home builds.
>       Go to http://www.ROV.net then ROV FAQ and look for 'Build your own ROV'.
> 
> 
> 




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